Abstract The cost of drug development has skyrocketed to an estimated $2.6B for every FDA approved drug primarily due to failures from lack of efficacy or safety, suggesting that our current preclinical validation process has been insufficient in predicting therapeutic potential and toxicity in humans. Animal models are the gold standard for dissecting disease mechanisms and evaluating novel drug targets in vivo; however, the cost and long lead time to develop them has prevented their routine use in the drug discovery process. With the recent developments in CRISPR/Cas9 genome editing, and advances in RNA interference technologies, we now have the ability to rapidly develop animal models with precise genomic modifications, and human-like disease pathologies. We have shown that RNAi serves as a fast alterative to gene deletion and can also be used within genetically engineered mouse models to assess the therapeutic potential and predict toxicities of novel gene targets. The goal of this proposal is to expand our capabilities beyond mice and develop a platform for rapid and cost-effective production of RNAi rats in as little as 4 months. Despite the utility of mouse models, for many scientists, the rat still remains the preferred rodent due to their larger size for surgical manipulation, repeat blood sampling, and their cognitive and physiological characteristics that more closely resemble humans than their mouse counterparts. For neurobiology, cardiobiology, immunology and toxicology, they are still the dominant rodent model in research. Nearly 20% of our current client base has inquired about rat models over the last 5 years, noting that most toxicology studies of their compounds are still done in rats prior to Phase I. We believe that rats will gain popularity once again as the premier rodent model in drug discovery and we intend to be at the forefront of this shifting paradigm. CRISPR/Cas9 genome editing now provides a path for manipulating the rat genome; however, current approaches enable the derivation of permanent gene knockout alleles, but do not allow temporal and reversible gene regulation. Our goal is to draw from our vast experience of mouse model creation and exploit the efficiency of CRISPR-based targeting to develop RNAi rat models that enable inducible and reversible gene silencing to simulate therapeutic regimes. These RNAi rat models will transform the preclinical validation process with assessment of potential drug response and resistance mechanisms in vivo, ultimately guiding the development of safer and more effective drugs.